ok(X,Y) :- between(100,200,X), between(100,200,Y).
ok(X,Y) :- between(200,300,X), between(200,300,Y).
ok(X,Y) :- between(400,500,X), between(200,300,Y).
ok(X,Y) :- between(800,900,X), between(300,400,Y).

run(X,Y) :- (ok(X,Y) -> print(user_output, 'true.\n'); print(user_output, 'fail.\n')).
